1. Field of the Invention
The present invention is in the field of electronic remote control devices for operating equipment at a distance.
2. Description of the Related Art
The present invention is specifically related to remote control systems that include a remote control transmitter having a transmitting device for remote control signals, an encoder circuit, and manual control elements. Such remote control systems further include a remote control receiver having a receiving device for remote control signals and a decoder circuit. Such remote control systems are used for industrial applications (e.g., to control cranes), but are also increasingly being used in the private sector (e.g., as simple garage door control systems or sophisticated remote control systems for television sets, or the like).
In Yoshikazu Tsuboi, et al., "MICROCOMPUTER-BASED REMOTE CONTROL SYSTEM FOR TV RECEIVERS," IEEE Transactions on Consumer Electronics, Vol. CE-25, November 1979, pp. 731-739, a remote control system is described which can deliver sixteen different commands for controlling a television receiver. The control signals are conveyed by infrared light. The remote control transmitter includes a keyboard comprising sixteen keys, a microcomputer used as an encoder circuit and a transmitting device containing a light-emitting diode ("LED"). The depression of one of the keys on the keyboard initiates the transmission of an encoded sequence of infrared light pulses. The light pulses are received by the remote control receiver in the television set by means of a receiving device that includes PIN photodiode. Immunity to interfering signals at the receiver is achieved by optical filters, selective amplification, averaging, and a Schmitt trigger circuit following the averaging device. The output of the Schmitt trigger is coupled to a microcomputer for decoding the received signals. The microcomputer delivers individual control signals (e.g., for channel selection).
A disadvantage of such remote control systems is the direct assignment of each remote control command to a single control key, because the number of keys increases with the number of control functions. Multiple use of the keys is unsatisfactory, too, because the tradeoff for the smaller number of keys is potential ambiguity and more complicated command entry. In addition, because of the small size of the usually hand-held remote control transmitter, it is hardly possible to represent the individual functions by symbols, even less so if the keys are used for multiple functions. In the case of television receivers, the operation of the transmitter is complicated by the fact that the environment is relatively dark, which makes it even more difficult to discern small unlit symbols.